1. Field of the Invention:
The present invention relates to a resin material supply apparatus and method for resin press molding machines.
2. Description of the Prior Art:
Conventionally, as shown in FIG. 7, there has been known a resin material supply apparatus which supplies resin material on a metal mold of the resin press molding machine such as a SMC molding press and so on.
Namely, in FIG. 7, a reference numeral 1 denotes a resin press molding machine, which includes a fixed lower metal mold 2 and an upper metal mold 3 provided movable in an up-and-down direction. A reference numeral 4 denotes a resin material. A reference numeral 5 denotes a resin material supply apparatus, which comprises a shiftable table 6, a supply cylinder 7 provided horizontally on the shiftable table 6, a piston 8 extruding the resin material 4 in the supply cylinder 7, a die 9 having an opening 9A for forming the resin material extruded from the supply cylinder by the piston 8 in a predetermined configuration, and a charge device 11 charging the resin material 4 in the cartridge 10 into the supply cylinder 7.
The piston 8 is connected through a piston rod 12 to an extrusion cylinder 13, and is slidable in the supply cylinder 7 by expansion and contraction of this extrusion cylinder 13. The die 9 is connected through a cylindrical body 14 to the front end of the supply cylinder 7, and a shutter device 16 is provided between the cylindrical body 14 and the die 9 so as to open or close a resin passage formed therein. The shutter device 16 comprises, as shown in FIG. 8, a shutter plate 19 having a hole 18, and a shutter cylinder 20 actuating this shutter plate 19 to slide in a transverse direction. In front of the die 9, there is further provided a cutter device 22 with a cutter 21 cutting the resin material 4.
The charger device 11 comprises a charge hopper 23 installed on the supply cylinder 7, a housing 24 holding the cartridge 10 so as to be extractable and retractable on the hopper 23, and a charge piston 25 charging the resin material 4 in the cartridge 10 on the hopper 23 into the supply cylinder 7. And the piston 25 is provided movable in an up-and-down direction by the a charging cylinder 26. Between the supply cylinder 7 and the charge hopper 23, there is provided a shutter device 27 so as to close their communicating passage. This shutter device 27 is constituted in substantially the same manner as the shutter device 16.
When the resin material 4 is to be supplied to the lower metal molding 2, the resin material 4 in the cartridge 10 is extruded by the piston 25 so that the resin material 4 is charged into the supply cylinder 7. In this instance, the shutter device 27 is opened, and to the contrary, the shutter device 16 is closed. Subsequently, the shutter device 27 is closed and the shutter device 16 is opened and, in turn, the resin material 4 in the supply cylinder 7 is extruded through the die 9 onto the lower metal molding 2 by the piston 8.
In such a conventional supply apparatus, there was the following practical problem since the shutter device 16 is provided in an intermediate portion of the resin passage 15. That is, after the resin material 4 is extruded onto the lower metal mold 2, the resin material 4 is cut by the cutter device 22. On the other hand, the shutter device 16 closes the shutter plate 19 in order to partition the resin material 4 remaining in the resin passage 15. For this process, if the resin material 4 is extruded onto the lower metal molding 2 in the next cycle newly extruded resin material 4 comes out in a shape separated into sheets because the cutting edge remained in the resin material 4 induces the division of the resin material during its extrusion.
Accordingly, if such a resin material 4 is fabricated in the resin press molding machine 1, the occurrence of a weld mark is increased. Therefore, strength of the molding product becomes weak at the places where weld marks are produced and the number of defective products will be increased.
On the other hand, if the shutter device 16 is completely removed, the resin material 4 in the resin passage 15 is no longer be cut. Therefore, it is possible to suppress the occurrence of weld marks and to obtain good quality products.
However, there will be caused a new problem in the case that the shutter device 16 is removed from the resin passage 15. That is, since the shutter device 16 is constructed such that it receives resin pressure when the resin material 4 is fed by the charge cylinder 26, the resin pressure comes to act directly on the flat-plate shaped cutter 21 of the cutter device 22 because of no shutting means in the resin passage 15. Especially, when the resin material 4 is charged into the supply cylinder 7, it is found that, by applying resistance on the extrusion cylinder 13 to cause back pressure against the piston 8, air or gases remaining inside of resin passage 15 can be scavenged nicely to enable manufacture of good products. For this reason, back pressure is set as high as possible, and resin pressure in the supply cylinder 7 becomes higher in accordance with this back pressure increase. Thus, the cutter 21 is pushed forward by this higher resin pressure.
On the other hand, since the cutter 21 needs to slide in front of the die 9 in an up-and-down direction, there are normally provided guides 30 (refer to FIG.4) at both ends. In this case, there are inherently formed gaps between these guides 30 and the cutter 21.
Accordingly, when the resin pressure is applied, there is caused a gap between the cutter 21 and a supporting plate 29 provided in front of die 9, and the resin material 4 is unexpectedly leaked through such a gap. Furthermore, if glass fibers included in the resin material 4 enter and are stuck in the gap, cutting operation of the resin material becomes worse. It is thus necessary to stop the machine to remove the glass fibers and clean up the cutter 21.
As a solution for such a problem, it may be considered to shorten the gap or to increase plate thickness in order to prevent the cutter 21 from being bent, however, its effect will be limited one.
Moreover, it is also found that a wide sheet width of the molded resin material 4 coming out from the opening 9A of the die 9 is preferable for molding operation therefore the current width of the molded resin material 4 is increased from 200 mm to 400 mm, and further considered to be widened to 600 to 800 mm.
Therefore, in accordance with such a width increase of the molded resin material 4, the cutter 21 increases its flat plate shape without increasing its width. By this shape modification of the cutter 21, it will be likely to cause bending to increase the gap, thus, it is predicted that the leakage of the resin material 4 will be greatly increased as a result.